For example, as shown in Patent Document 1, a uniflow-scavenging-type two-cycle engine (two-stroke engine) used also for an engine of a ship has an exhaust port provided at a first end of its cylinder in the stroke direction of its piston and has scavenging ports provided at a second end of its cylinder in the stroke direction of its piston. When, in the intake (induction) process, an active gas is drawn in from the scavenging ports to a combustion chamber, an exhaust gas generated by the combustion action is exhausted, as if being pushed out, by the drawn in active gas.
At this time, a premixed gas is generated by injecting a fuel gas to the drawn in active gas, and the generated premixed gas is compressed. Then, in the compressed premixed gas, a pilot fuel is injected, to thereby obtain a combustion action of the premixed gas ignited by the combustion of the pilot fuel. With an explosive pressure generated by the combustion action, the piston reciprocates in the cylinder. To achieve this, the cylinder is provided with a fuel injection valve that injects a fuel gas. However, in two-cycle engines with a large diameter such as two-cycle engines for ships, a plurality of fuel injection valves are provided in the circumferential direction of the cylinder, and the fuel gas is injected simultaneously from the fuel injection valves.